The invention relates generally to sealants and more particularly to thread sealant compositions, their method of manufacture and their use.
Thread sealants can be used by plumbers to form a tough, pliable film on threaded pipes and valve connections, flanged surfaces, gaskets and bolts to provide a leak-proof resistance to high pressure and temperature, expansion, contraction and extreme vibration. Thread sealants have long been used by the plumbing industry to provide leak-proof resistance to threaded joints, pipes, gaskets, flanges and couplings. Traditional thread sealant is composed of hydrocarbon oils, vegetable oils, animal oils, fillers and fibers. Alternative materials for sealing threads include Teflon tape, paper and rubber products or anaerobic chemicals.
Gaskets and paper products relax and can form a minute separation or leak path. Solvent based thread sealants, often referred to as pipe dope sealants, rely on solvents and natural fibers. Once the solvent evaporates, the uneven character of the natural fibers and filling materials can also lead to minute leak paths. Teflon tape is often used where there is over tightening of the seal and may shred, leading to leaks or downstream pipe contamination. Anaerobic thread sealants, once cured, are difficult to remove from a pipe thread. For all of these thread sealant approaches, leaks may still occur due to system vibrations, thermal cycling, pulsing of liquid or gas contents, poor application or improper thread design. Leaks from these sources cost millions of dollars a year in lost material, damage to the environment and inefficient use of the transferred material.
Conventional thread sealants exhibit several additional disadvantages. They are typically not smooth and can be difficult to apply evenly and uniformly to pipes. Conventional sealants do not generally offer consistent performance from batch to batch and have a high propensity for leakage at high pressure and temperature because of the inconsistency in the structure of the fibers included. For example, solvent based thread sealants typically include fillers made of inorganic minerals, such as clays, calcium carbonate and fibrous material to enhance the resistance to high pressure leakage. The fibrous materials typically include natural organic matter, such as wool or leather and synthetic fibers, such as polyfluoroethylene (PTFE). Sealants that include natural organic material lack consistency because of the variations in the density and length of the fibers, as well as variations in the fibers' ability to absorb and bind to solvents employed. Consequently, sealants produced have slightly different properties varying from batch to batch. Although synthetic fibers, such as PTFE, are more uniform, the resulting sealants tend to be too pasty and hard to apply most effectively.
Another drawback is the inability of clay/mineral based thread sealants to resist the pressure and temperature found in many applications, because the oil, fibers, and mineral fillers separate under pressure from either tightening of the threaded joints or the application of pressure within the pipe.
Another problem with conventional thread sealants is that they are not always sufficiently forgiving with respect to filling thread imperfections. In the average threaded fitting, metal to metal contact is approximately 20%. 80% is air space surrounding the spiral threads, creating a potential fluid or gas leak path. The size and scope of the path can be dramatically affected by vibration, shock, thermal and environmental changes. They can also be intolerant of poor application. Thread sealants utilizing natural fibers are also susceptible to mildew, aging and exposure to sunlight.
Traditionally, plumber's thread sealant uses high levels, usually between 6%-25%, of fibers and thickeners to improve the ability to withstand high pressure and/or temperature. However, the high levels of fibers produce a thick sealant with visible fibers, making the sealant more difficult to apply. The brushes used to apply the sealant to the pipe threads often wind up separating the fibers from the oils in the formulation leaving “clumps” of threaded material inconsistently spread around the threads and areas where there is far more oil than fiber. This can lead to leaks.
Accordingly, it is desirable to provide an improved thread sealant that overcomes drawbacks of conventional sealants.